August 2011 Professor Hammer’s Metalworking Tips

You can email your questions to Professor Hammer at covell@cruzio.com, or mail to Professor Hammer, c/o CLASSIC TRUCKS Magazine, 1733 Alton Pkwy., Irvine, CA 92606. You’ll receive a personal reply! We’ll print your name and city unless you request otherwise. Ron Covell has made many DVDs on metalworking processes, and he offers an ongoing series of workshops across the nation covering all aspects of metalworking. Check them out online at www.covell.biz, or call for a current schedule of workshops and their free catalog of DVDs. Phone 800-747-4631, or 831-768-0705. You can send a request by mail to: Covell Creative Metalworking, 106 Airport Blvd. #105, Freedom, CA 95019.

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Q: What are your thoughts on using the oxyacetylene style of brazing for fabricating operations—chopping tops, frenching headlights, shaving hoods, or pretty much every aspect of sheetmetal work? I have a lot of experience in that process from years past, putting together fairly intricate radio controlled race cars, and it works well for that application.

Ben Jones

Via the Internet

A: Brazing has been around for a very long time, and it has some characteristics that make it well suited for many applications. Brazing is an easy process to learn, and the oxyacetylene equipment required for brazing is less costly than for any type of electric welding. When brazing, it’s easy to build up a lot of material, as is sometimes needed for creating fillets, or filling low spots. Brass won’t rust, and that offers some benefits for certain types of work. It’s also a good material to use on parts that will be chrome plated, since the copper-nickel-chrome electroplating process works exceptionally well with brass. While brass isn’t quite as strong as steel, if you build up sufficient thickness, in some cases the brazed joint can be as strong, or stronger, than the base metal.

3/3Although not recommended for bodywork, brazing has many applications for building classic trucks. The process is easy to learn, and the equipment is quite affordable!

Unfortunately, there is one characteristic that limits the usefulness of brass for auto body work, such as frenching headlights, shaving hoods, or chopping a top; neither paint nor plastic filler stick to brass very well, so I really don’t recommend it for work of this nature.

If you’ve been around cars and trucks for some time, you’ve probably seen a lot of photos in old magazines that show custom cars and trucks being built with the bodywork brazed, since that was a common way of working “back in the day”. Now that I know the limitations of brazing on bodywork, if a car or truck comes into my shop with any body metal that has brass on it, I will cut that area out and replace it with new metal!

As an interesting sidelight, bronze filler rod is increasingly being used with MIG and TIG welding. Bronze is an alloy of copper and tin, while brass is an alloy of copper and zinc. Paint and plastic body filler stick pretty well to bronze, so many OEM manufacturers are using bronze-welded joints on certain body panels, and it’s becoming more accepted in the collision-repair trade, as well.

Q: Hello Ron, I enjoy your Q&A in Classic Trucks! I’m doing a partial doorskin replacement on a ’40 Chevy truck; what’s the best way to get that sharp edge on the new skin so that it will match the factory edge? I’m doing a partial replacement—the front third of the door—and the new skin has the 90-degree flange, but it has a lot of roll in the bend; it’s not really sharp. I’m thinking it may need some hammer work on the face of the door (after I fold over the flange) to make it match the factory edge. I don’t want to damage the face side by doing anything unnecessary or out of order.

Charles Snuffer

Via the Internet

A: Doorskins are held to the inner doorframe with a hemmed (folded over) edge. Normally, a replacement doorskin comes with a 90-degree flange on the outer edges. The flanged edges are placed over the inner doorframe, and then the flange is hammered down flat to make the hem, holding the skin to the doorframe. This gives the door edge a uniform, finished appearance.

The way I like to do this job is to lay the door upside down against a heavy, smooth-surfaced steel plate, and orient the door so there is no air gap under the section I’m hammering on. The hem is flattened out in that section, then the door is repositioned, and the process is repeated. This eliminates any problems of getting hammer marks on the outer surface of the doorskin.

The flatter you hammer the flange down when making the hem, the sharper the radius on the door edge, up to a limit. If the doorskin and the inner structure are made of 20-gauge steel, you just can’t get the “sandwich” of metal to be less than 1⁄8 inch (the thickness of three pieces of .035-inch sheet), which gives you a 1⁄16-inch edge radius. This is most likely the radius the original door has. CT